> And over the long run, sharing lawnmowers wouldn't even reduce total lawnmower production. The shared lawnmowers would run more hours per week and need replacement sooner.

This is only true if people fully utilize their personal lawnmower before discarding it. I doubt this is the case. It seems that sharing would result in less discarding of under-utilized lawnmowers, and thus reduce the number of lawnmowers needed. Of course, I'm not saying anyone should be forced to do this.